It may be desirable to provide a micro-fluid ejection device, for example, a printer, that is manually positioned over a media or substrate surface (such as a piece of paper, cardboard, cloth, wood, plastic, film, or similar material). The device may then be activated to eject fluid, such as ink, to provide text or graphical information on that surface. Ejection of ink in the manner described above is analogous to airbrush painting except that the pattern of ink from the ejection device is controlled to produce textual or graphic images instead of the simple spray “dot” or lines produced by an airbrush device. In such applications the ejection device is generally substantially physically unengaged from the media or substrate on which the fluid is deposited. In other words, the physical location, orientation, and motion of the surface and micro-fluid ejection device with respect to each other are not mechanically controlled either by the ejection device or by an external mechanism.
As used herein the term “orientation” refers to both spatial and dynamic orientations. A spatial orientation is a geometric orientation between an ejection head and a substrate surface irrespective of whether there is relative translational or elevational motion between the ejection head and the substrate surface. A dynamic orientation is a kinetic relationship between an ejection head and a substrate surface. A dynamic orientation is defined at least in part by a vector having a magnitude and a direction. The magnitude and the direction of vectors are each separately considered herein to be an element of orientation between an ejection head and a substrate surface. The dynamic orientation may represent a relative velocity or a relative acceleration between the ejection head and the substrate surface.
In order to compensate for the mechanical dissociation between the ejection device and the surface, one or more optical sensors may be incorporated into the ejection device to track the relative motion of the device as it moves over the surface of the material onto which the fluid is ejected. The foregoing is analogous to the tracking provided by an optical mouse in a computer system. Referential position information regarding the location of the ejection device with respect to substrate surface is provided by the optical sensor to the ejection device, and control circuitry in the ejection device uses this positional data to assist the user in determining when to eject fluid as the ejection device moves over the surface of the substrate.
While these hand-held micro-fluid ejection devices typically sense position over the substrate surface and may automatically determine when an area traversed should be imprinted, the motion of these devices is controlled by the operator whose motion may be random, irregular, and inconsistent. Such unpredictable motion contrasts sharply with traditional printers where motion is precisely controlled, so the hand-held design has unique challenges in compensating for the motion of the operator to maintain quality of the imprinted image. What are needed are apparatuses and methods for dealing with operator motion that exceeds desired design limits. Examples include: print motion outside optimal speed; excessive rotation or acceleration; excessive yaw angle; and separation of the ejection head from the substrate surface.
Exemplary embodiments of the disclosure provide a hand-held micro-fluid ejection device for ejecting a fluid onto a substrate surface in a plurality of physical orientations between the ejection device and a substrate surface. The device typically incorporates an ejection head that has an enabled state for permitting the ejection of the fluid onto the substrate surface and a disabled state for blocking the ejection of the fluid onto the substrate surface. A position sensor system is typically included. The position sensor system is configured to provide measured data indicative of an actual orientation between the ejection device and the substrate surface. Generally an electronic processor is provided, and the electronic processor is configured to receive the measured data from the position sensor system and configured to place the ejection head in the disabled state if the measured data indicates that the actual orientation of the ejection device exceeds a threshold limit for the orientation between the ejection device and the substrate surface.
Some embodiments provide a hand-held micro-fluid ejection device for ejecting a fluid onto a target area of a substrate surface that includes an ejection head that has an enabled state for permitting the ejection of the fluid onto the substrate surface and a disabled state for blocking the ejection of the fluid onto the substrate surface. A position sensor system is provided, and the position sensor system is configured to provide measured data indicative of a location of the ejection device with respect to the target area of the substrate surface. An electronic processor is included, and the electronic processor is configured to receive the measured data from the position sensor system and configured to place the ejection head in the disabled state if the measured data indicates that the location of the ejection device is not within the target area.
Methods are provided for controlling the geometric accuracy of printing using a hand-held printing apparatus. In exemplary applications the method includes a step of acquiring in the printing apparatus at least one threshold limit representing a maximum value for an orientation parameter affecting the spatial accuracy of printing on a target area of a printing surface. The method generally further includes a step of sensing a print signal that if positive indicates an operator's instruction to print a portion of an image using the printing apparatus, and a step of sensing an orientation of the printing apparatus relative to the target area of the printing surface. The method typically further includes a step of disabling the printing by the printing apparatus if the orientation of the printing apparatus relative to the target area of the printing surface exceeds the threshold limit when the print signal is positive.